For an operator, the first step to rollout a radio network is to build macro BSs to guarantee basic coverage. There is normally no high capacity requirement at the initial rollout phase. When the network evolves, however, more and more User Equipments (UEs) will be served by the network. Capacity extension will be required for some BSs. There are in general three main solutions as listed below to improve macro deployment with capturing capacity demand. FIG. 1 shows a schematic diagram of the three solutions.                Improve Macro        Improve macro capacity by for example adding more carriers. This method is normally the cheapest solution for those operators who have enough radio bandwidth resources, since there is no requirement for more sites as compared to the Densify Macro solution discussed below. Hence Capital Operating Expense (COPEX) increases not too much. For example, for CMCC, there is currently 50 MHz bandwidth for a TD LTE network rollout. Therefore, adding multiple carriers used for macro base station capacity improvement is a good choice for CMCC.        Advantage: it is cheap if the operator has enough radio resources.        Disadvantage: large radio bandwidth resources are needed.        Densify Macro        Increase the number of macro BSs for a certain area with smaller Inter-Site Distance (ISD). In the solution, time-frequency resources can be reused in spatial domain with more macro BSs deployed. However, this leads to more COPEX for operators since operators need to find more sites to deploy BSs and more BSs to be deployed. The solution also brings a challenge in network optimization.        Advantage: Do not need large radio bandwidth resources.        Disadvantage: COPEX is highest among the three solutions.        Add Small Cells        This method can be viewed as an enhancement of the Densify Macro solution, namely heterogeneous network deployment, where Pico BSs with a lower transmission power are dedicated to providing services for hot-spots on top of Marco deployment. Similarly as the Densify Macro solution above, it also increases the number of BSs to be deployed. It is thus an expensive solution especially compared with the Improve Macro solution. The BSs deployed have a lower transmission power, and thus the solution has a lower COPEX compared with the Densify Macro solution. Furthermore, the performance of the solution is sensitive to whether the Pico BSs are correctly put to real hot-spot(s). Accordingly, the gain brought out by the solution may be low when the hot-spot changes as the UEs within the hot-spot move.        Advantage: Do not need large radio bandwidth resources.        Disadvantage: COPEX is relative high.        
From the above outline, it can be seen that the Improve Macro solution is the most efficient way among the three solutions to improve network capacity, which can efficiently avoid the disadvantages of a high COPEX of the Densify Macro and Add Small Cells solutions.
In a radio network, UEs are moving around all the time. FIG. 2 shows a schematic diagram of the robustness of the three solutions in a UE movement scenario.
As can be seen from FIG. 2, the UEs can be well served as they move in the Improve Macro solution which adds more carriers to cover the whole cell. In the Densify Macro solution, more macro BSs are added to share and balance the load within the cell. However, some of the macro BSs may be overloaded since the UEs may converge at a position in the cell as they move. The Add Small Cells solution puts Pico BSs to serve hot-spots. When the UEs in the hot-spot move, the hot-spot moves or changes. As shown in FIG. 2, the hot-spot may move out of the coverage of the Pico BS deployed previously. Therefore, the Densify Macro and Add Small Cells solutions are not the efficient way to provide good enough services for moving UEs. The intended network capacity enhancement is not well satisfied for the two solutions in such moving scenarios.
In the Improve Macro solution, each carrier shall be allocated with the same power for covering the whole cell so that the network capacity enhancement obtained by adding more carriers is ensured even if the UEs move. FIG. 3 shows a schematic diagram of an Improve Macro solution where carriers are allocated with different power. Carriers shown in the dotted area are allocated with smaller power to serve the newly emerged UEs that are close to the BS. When the new UEs move away, the network capacity enhancement obtained by adding the carriers disappears. Allocating each carrier with the same power sufficient for covering the whole cell can avoid such case. However, ensuring multiple carriers with the same coverage of the whole cell will result in the inefficiency of the total transmission power, and increase the cost. For example, assume that 40 W for each carrier of 20 MHz bandwidth is required for macro coverage. If 3 carriers with 60 MHz bandwidth is to be supported in the Macro cell, 120 W output power is needed, which means:                Much higher component cost.        Larger RRU size and weighting due to heating requirement.        Lower power efficiency when the Macro BS stays in a low transmission power condition (for example in midnight, there is low load).        
Therefore, there is still a need to effectively enhance network capacity with a relative low transmission power requirement.